1. Field of the Invention
The present invention relates to the field of integrated circuits, and more particularly, to a method and apparatus for improved interconnections between an integrated circuit and a data processing system.
2. Description of the Related Art
Integrated circuit (IC) cards (also referred to as electronic function cards) are used with data processing systems to provide increased functionality for the data processing system. IC cards may be used for many purposes such as providing additional memory with a memory card or providing digital storage for such applications as cameras and mobile telephones. IC cards may also provide communication capabilities for a data processing system with external data processing systems or networks by functioning as a modem card, a facsimile card, a local area network (LAN) interface card, and/or a multimedia interface card. The IC cards provide convenience for users in allowing the user to install as needed or desired additional capabilities or features for the data processing system.
IC cards are generally portable cards, often referred to as small form factor cards, that may be inserted into and detached from a receptacle within the data processing system. The small form factor card dimensions are designed to correspond with the particular receptacle into which they will be inserted. Although leads may be soldered between the card and the data processing system, more typically the card has a connector built in and the card is inserted into a receptacle of the host data processing system (also referred to as a host socket). Once inserted into the receptacle of the data processing system, an electrical interface is made between the card connector and the data processing system allowing for communication between the card components and the data processing system.
The IC card itself generally contains a printed circuit board (PCB) attached to a connector, which serves as the IC card connector, with an IC package then mounted on the PCB. Metallized lines on the PCB allow communication between the IC package and the card connector. In electrically connecting the IC package to the PCB, there are typically two levels of interconnection involved. First, an IC die is enclosed within an insulating housing that includes a lead frame having a plurality of leads extending externally from the housing to form an IC package. The leads may be either pins extending from the housing or bump leads on the surface of the housing. The leads are internally coupled to the IC die and permit the IC die, now encased within the housing, to couple to and communicate with other devices. The second level of interconnection provides an electrical connection of the IC package and connector to the PCB.
There are different methods of coupling the IC package to the PCB. One standard method, referred to as surface mount technology (SMT), is typically used with a thin small outline package (TSOP). With SMT, the TSOP leads are directly soldered to the PCB. The leads must be placed at the desired location on the PCB and then soldered to the PCB. The coplanarity between the leads and the PCB must be tight, and the location of the leads on the PCB must be accurate. Even with robotics performing the soldering process, the time and expense necessary to ensure a workable interconnection between the IC package and the PCB is great.
When soldering an IC package to a PCB, there is a substantial amount of testing required due to the multiple steps involved in assembling the IC card. First, there is a wafer level test on the IC die. Then, after the IC die has been encased in a housing to form an IC package, the connection between the IC die and the leads of the IC package must be checked. Once the IC package and connector are mounted on the PCB, the connections between the leads on the IC package and connector and the metallized lines of the PCB are tested to ensure that nothing was damaged in the soldering process. After the PCB and the IC package and connector mounted thereon are encased in a card casing to form an IC card, the IC card is tested to ensure a workable electrical interface between the components on the PCB and the receptacle of the data processing system. Often, the tests of the connection between the IC package and connector and the PCB and the final IC card product may be done simultaneously in a single step. Thus, as many as four separate testing phases may be required to ensure that the IC die can effectively communicate with the data processing system.
The present invention describes an IC card that eliminates the PCB entirely by allowing the leads from the IC package to serve as the electrical interface between the IC package and the card connector, which is now independent of the PCB. Because a PCB is no longer required to make the connection between the IC package and the data processing system, the manufacturing step of soldering the IC package on to the PCB is eliminated. By eliminating the need for soldering the IC package to the PCB, less material will be used, fewer leads will be damaged, and time will be saved during assembly. Additionally, eliminating the interconnection of the IC package to the PCB eliminates a testing step also. Thus, the elimination of the PCB within the IC card improves the IC card's reliability while simultaneously decreasing both the expense and time associated with assembling the IC card.